1. Field of the Invention
The present invention relates to a detection unit for detecting the residual amount of developer, and a developer vessel, a developing cartridge, and a process cartridge, which use the detection unit respectively, and an electrophotographic image forming apparatus to which the process cartridge is detachably attachable.
2. Related Background Art
The electrophotographic image forming apparatus forms an image on a recording medium by using an electrophotographic image forming method. Examples of the electrophotographic image forming apparatus are an electrophotographic copying machine, electrophotographic printer (e.g., laser beam printer or LED printer), a facsimile apparatus, and a word processor.
The process cartridge is a cartridge which is an integral unit of at least a developing member and electrophotographic photosensitive drum and is detachably attachable to the main body of the electrophotographic image forming apparatus.
A conventional electrophotographic image forming apparatus using an electrophotographic image forming process adopts a process cartridge method in which an electrophotographic photosensitive member and a process means which acts on the electrophotographic photosensitive member are integrated into a cartridge and this cartridge is detachably attachable to the main body of the image forming apparatus. According to the process cartridge method, the apparatus can be maintained not by the serviceman but by the user, greatly improving the operability. This process cartridge method is widely used in image forming apparatuses.
The process cartridge forms an image on a recording medium with a developer, and consumes the developer every time an image is formed.
Some image forming apparatuses comprise a developer amount detection device which notifies the user that the developer has run out.
A conventional developer amount detection device has two electrode bars within the developer vessel of a developing member, and detects a change in electrostatic capacitance between the two electrode bars to detect the developer.
Japanese Patent Application Laid-Open No. 5-100571 discloses a developer amount detection device having a developer detection electrode member which is obtained by interdigitating, in concavo-convex form, two electrodes arranged parallel to each other at a predetermined interval on the same plane, instead of two electrode bars, and is set on the lower surface of the developer vessel. This apparatus detects the residual amount of developer by detecting a change in electrostatic capacitance between the parallel electrodes set in the flat state.
U.S. Pat. No. 6,253,036 discloses a detection device which sequentially detects the residual amount of developer by using an electrode member obtained by interdigitating, in concavo-convex form, two electrodes arranged parallel to each other at a predetermined interval on the same plane.
FIG. 25 shows attachment of a detection member 20 for sequentially detecting the residual amount of developer. An adhesion surface 29c for the detection member 20 is flat, and the detection member 20 is adhered to the entire adhesion surface 29c. If this arrangement is left at high temperatures and high humidities, the adhesive of the detection member 20 may float from the adhesion surface to generate bubbles. This phenomenon occurs due to a large adhesion area. Generated bubbles allow the toner to flow into the backside of the detection member 20, or change tight contact with the adhesion surface. As a result, the electrostatic capacitance detected by the detection member 20 varies.
The arrangement shown in FIG. 25 is devised under the development of the present invention, therefore is not a prior art.
It is an object of the present invention to provide a process cartridge, a developing cartridge, a developer vessel, and a detection unit, which are capable of accurately detecting the residual amount of developer, and an electrophotographic image forming apparatus to which the process cartridge is detachably attachable, and an electrophotographic image forming apparatus to which the developing cartridge is detachably attachable.
It is another object of the present invention to provide a process cartridge, a developing cartridge, a developer vessel, and a detection unit, which are capable of preventing a developer from attaching to the reference electrode member of a detection unit, and an electrophotographic image forming apparatus to which the process cartridge is detachably attachable, and an electrophotographic image forming apparatus to which the developing cartridge is detachably attachable.
It is still another object of the present invention to provide a process cartridge, a developing cartridge, a developer vessel, and a detection unit, which are capable of reliably adhering a measurement electrode member to an adhesion member, and an electrophotographic image forming apparatus to which the process cartridge is detachably attachable, and an electrophotographic image forming apparatus to which the developing cartridge is detachably attachable.
It is still another object of the present invention to provide a process cartridge, a developing cartridge, a developer vessel, and a detection unit, which are capable of reliably adhering the reference electrode member to the adhesion member, and an electrophotographic image forming apparatus to which the process cartridge is detachably attachable, and an electrophotographic image forming apparatus to which the developing cartridge is detachably attachable.
It is still another object of the present invention to provide a process cartridge, a developing cartridge, a developer vessel, and a detection unit, which are capable of easily positioning a detection unit for detecting the residual amount of developer within a developer vessel with respect to the developer vessel, thereby increasing the assembly precision, and an electrophotographic image forming apparatus to which the process cartridge is detachably attachable, and an electrophotographic image forming apparatus to which the developing cartridge is detachably attachable.
According to an aspect of the present invention, there are provided: a detection unit for outputting an electrical signal in accordance with an electrostatic capacitance to an apparatus main body in order to detect a residual amount of developer in an electrophotographic image forming apparatus main body, comprising:
a measurement electrode member which is arranged at a position where the measurement electrode member contacts the developer when mounted in the developer vessel, has at least a pair of portions parallel to each other at a predetermined interval, and has an input electrode for receiving a voltage from the apparatus main body and an output electrode for outputting an electrical signal in accordance with an electrostatic capacitance generated upon application of the voltage;
a reference electrode member which is arranged at a position where the reference electrode member does not contact the developer when mounted in the developer vessel, has at least a pair of portions parallel to each other at a predetermined interval, and has an input electrode for receiving a voltage from the apparatus main body and an output electrode for outputting an electrical signal in accordance with an electrostatic capacitance generated upon application of the voltage;
an adhesion member to which the measurement electrode member is adhered;
a lid member which is coupled to the adhesion member and covers the reference electrode member interposed between the adhesion member and the lid member; and
an engaging portion which engages with a vessel positioning portion when the detection unit is attached to the developer vessel, and positions the detection unit with respect to the developer vessel, and
a developer vessel, a developing cartridge, and a process cartridge, using the detection unit which use the detection unit respectively, and an electrophotographic image forming apparatus to which the process cartridge is detachably attachable.